Ambient PM2.5 Exposure and Population Health in Nigeria: Trends and Public Health Implications
Background: Fine particulate matter (PM2.5) remains a major environmental health concern, particularly in low- and middle-income countries. Nigeria experiences persistently high ambient PM2.5 exposure, yet long-term national evidence linking annual exposure patterns with broad population-health indicators remains limited. Objective: To examine trends in population-weighted ambient PM2.5 exposure in Nigeria from 1990 to 2023 and assess ecological associations with life expectancy, under-five mortality, and crude death rate. Methods: An ecological time-series study was conducted using 34 annual observations from the World Bank World Development Indicators. Population-weighted PM2.5 exposure was the principal exposure. Health outcomes were life expectancy, under-five mortality, and crude death rate. Urban population percentage and GDP per capita were included in sensitivity analyses. Descriptive statistics, linear trend models, Pearson correlations, ordinary regression diagnostics, and autoregressive integrated moving average (ARIMA) models were used. Results: Mean PM2.5 exposure was 62.97 ± 5.22 µg/m³ and showed no significant linear trend over the study period (B = -0.016 µg/m³/year, p = .863). Life expectancy increased significantly, while under-five mortality and crude death rate declined significantly (all p < .001). Crude correlations between PM2.5 and the three health outcomes were not significant. Final ARIMA(1,2,0) models showed no significant PM2.5 association with under-five mortality (B = -0.003, p = .715), life expectancy (B = 0.008, p = .074), or crude death rate (B = -0.005, p = .108). Findings remained non-significant after adjustment for urbanisation and GDP per capita, and final model residual diagnostics were acceptable. Conclusions: Nigeria experienced persistently high PM2.5 exposure alongside marked improvements in selected population-health indicators. Annual national PM2.5 variation did not independently explain these broad health outcomes after serial dependence was modelled. Stronger air-quality surveillance and more spatially resolved, disease-specific epidemiological studies are needed.